1. Field of the Invention
The present invention relates to a highly transparent silicone fluid composition, and in particular to a highly transparent silicone fluid composition which has a light transmittance of 90% or greater when filled into a 10 mm-thick quartz cell and subjected to visible light of any wavelength, and is, therefore, useful in the production of articles such as optical fibers, optoelectronic products, optical instruments, etc.
2. Discussion of the Background
JP-A-50 64 354 teaches a transparent silicone fluid compound mainly composed of a methylphenylpolysiloxane and a fumed silica having similar refractive indices, and mixed with various additives such as oxyalkylenes and polyoxyalkylenes. Such silicone compounds may also contain HO(CH.sub.3 C.sub.6 H.sub.5 SiO).sub.n H or a dimethylpolysiloxane and a silica whose surface is treated with an organosilicic compound such as [(CH.sub.3).sub.3 Si].sub.2 NH.
JP-A-51 86 558 teaches a compound composed of a methylphenylpolysiloxane containing 29-34 wt. % phenyl groups, and additives such as an untreated fumed silica, an untreated precipitated silica, and a stabilizer. JP-A-2 45 561 teaches a compound composed of a methylphenylpolysiloxane containing 5-30 mol % phenyl groups, and additives such as a fumed silica whose specific surface area is no less than 130 m.sup.2 /g, diphenyldialkoxysilane and diphenyldichlorosilane. JP-A-61 246 292 teaches a compound composed of a methylphenylpolysiloxane containing 5-20 mol % phenyl groups, additives such as a fumed silica whose specific surface area is no less than 130 m.sup.2 /g, and an alkoxysilane containing either a double bond or an epoxy group.
Most of these known silicone fluid compositions contain methylphenylpolysiloxanes as the base material, are highly transparent and undergo minimal oil bleed. However, most of these compositions fail to exhibit a light transmittance of 90% or greater when filled into a 10 mm-thick quartz cell and subjected to visible light of certain wavelengths. The silicone fluid compound described in JP-A-61 246 292 undergoes virtually no oil bleed and has excellent light transmittance (greater than 90% in the case of 10 mm-thickness) and is, therefore, extensively used in optical fibers, optoelectronic products, optical instruments, scintillation camera, etc., and would be used as much in other applications if its cost were lower.